1. Field of the Invention
The present invention relates to a cylinder assembly for a compressor that is used in refrigeration system like refrigerators, air conditioners, or the like.
2. Description of the Prior Art
Generally, a refrigeration system like refrigerators or air conditioners employ a hermetic compressor, and as shown in FIGS. 1 and 2, the hermetic compressor 10 includes an electric rotation driving unit 20 that has a rotor 21 and a stator 22, a cylinder assembly 30 that compresses refrigerant by the movement in association with the electric rotation driving unit 20 and then discharges the compressed refrigerant, and a casing 11 that houses the electric rotation driving unit 20 and the cylinder assembly 30.
The cylinder assembly 30 includes a cylinder block 31, a cylinder head 32 and a valve plate 35.
The cylinder block 31 has a cylinder 31a formed therein, the space in which the refrigerant is drawn in through a refrigerant suction passage. The refrigerant is compressed as the rotor 21 is rotated and a piston 25 is accordingly reciprocated within the cylinder 31a in a linear direction.
The cylinder head 32 is disposed at a side of the cylinder block 31 to seal an open end of the cylinder 31a. As the cylinder head 32 is connected to the cylinder block 31, a refrigerant suction chamber 37 and a refrigerant discharge chamber 36 are defined between the cylinder block 31 and the cylinder head 32. The refrigerant suction chamber 37 is connected with a refrigerant suction passage, while the refrigerant discharge chamber 36 is connected with a refrigerant discharge passage.
A valve plate 35 is disposed between the cylinder block 31 and the cylinder head 32, and has a refrigerant suction hole 35a and a refrigerant discharge hole 35b for connecting the cylinder 31a respectively to the refrigerant suction chamber 37 and the refrigerant discharge chamber 36.
The cylinder assembly 30 is provided with a suction valve 38a and a discharge valve 39 for selectively opening and closing the refrigerant suction hole 35a and the refrigerant discharge hole 35b while the piston 25 is driven. The operation of the suction valve 38a and the discharge valve 39 is depicted in detail in FIG. 2.
Referring to FIG. 2, as the piston 25 is moved to a lower dead end, refrigerant is drawn into the cylinder 31a. Here, the suction valve 38a is opened. Then as the piston 25 is moved to the upper dead end, the refrigerant is compressed. Here, the suction valve 38a is closed. As the pressure of the compressed refrigerant exceeds a certain point, the discharge valve 39 is opened, and the compressed refrigerant is discharged outside of the cylinder 31a. 
In the conventional cylinder assembly constructed as above, the suction valve 38a is closed during the refrigerant compression, hitting against the valve plate 35 directly. The refrigerant in the cylinder 31a flows at a much lower temperature than the atmospheric temperature. Accordingly, the suction valve 38a is constantly subjected to the low temperature and impulses, and as a result, damages like cracks occur in the suction valve 38a, deteriorating the durability of the compressor 10. Still another problem is that the leading end of the suction valve 38a is hit against the valve plate 35 and causes a noise in the high frequency range.